need help with my Toshiba l755 backlight

[new]

Re: need help with my Toshiba l755 backlight

everything was working fine till the laptop bricked due too a bad flash . then i gave it to someone he has the bios programmer , he programmed it and the laptop start to working and booting again like normal without backlight enabling ???

[new]

Re: need help with my Toshiba l755 backlight

can someone please provide me with the right EC firmware bios file ??

[luke10050]

Re: need help with my Toshiba l755 backlight

It might take people a bit of time to respond, unless its included in the standard bios package from toshiba it may not be easy to find and may take a while

[new]

Re: need help with my Toshiba l755 backlight

Ok thanks

[khaahk]

Re: need help with my Toshiba l755 backlight

And provide some detail about the model, for example L755-xxxx or toshiba model nr PSCxxxx.

[new]

Re: need help with my Toshiba l755 backlight

i re flashed the bios again but still the same problem . i believe now it is something in the motherboard . but i can't figure out it

[new]

Re: need help with my Toshiba l755 backlight

some people saying it is a fuse issue . i have checked pf2 fuse and it is ok . is there any other fuses to check ?

[new]

Re: need help with my Toshiba l755 backlight

i gave up

[khaahk]

Re: need help with my Toshiba l755 backlight

Are you able to check voltages? Pin 20, 22,23 lvds connector? With laptop turned on. Carefully.
Fuse pf2 is connected to battery in your case, has nothing to do with blight.
Backlight is driven by pch.

[new]

Re: need help with my Toshiba l755 backlight

it took too much time to TS this laptop and nothing working . i scraped it . thx everybody

[ktmmotocross]

Re: need help with my Toshiba l755 backlight

khaahk> LCD is driven by KBC/DISPON_O/ and PCH/LVDS_VADJ/


dont give up. its easy fault.
Check for voltage on LCD signals LCDVCC, LVDS_VADJ, DISPON_O and LCD_BK_POWER on power on laptop

[dj_ricoh]

Re: need help with my Toshiba l755 backlight

EC usually has output that drives the backlight enable circuit. Sometimes just this output of ec is dead, then the laptop will work fine otherwise.
If the schematics is correct, then DISPON signal is not driven by EC in your case

EEEEEEEEE! Wrong ! DISPON_I pin 27.

if the screen was attempted to be replace with battery ON then it will cause a short to KBC : no backlight or full dead

swap the KBC NUVOTON NPCE791LA0DX and your good to go.

[khaahk]

Re: need help with my Toshiba l755 backlight

Pin 27 is input from PCH, backlight is turned on by EC pin 6, does it require pin 27 from PCH to be high or not, that is a good question...

[ktmmotocross]

Re: need help with my Toshiba l755 backlight

yes. DISPON_O - 3.3V, LVDS_ADJ - 0V-3.3V/3.3 is full light/

[highpulse]

Re: need help with my Toshiba l755 backlight

very common on this machine to fail the PCH , for video issues , loosing sound after a while , camera getting hot .. for my experience and for the incoming machines we've got per day , 80% of the l755 problems are related to pch

[Joseph cauchi]

Re: need help with my Toshiba l755 backlight

Just a simple question is the back light CCFL or LED?
If the back light is ccfl change the inverter.